Our company relies heavily on Public Calendars in the Exchange Public Folders and the ability to view these public calendars on mobile devices. I am sure many of you are aware of the issue of not being able to view public calendars with the Exchange Sync on an iPhone.

Well, we came up with a solution that works, for the most part, however, we are having one problem that we just can’t figure out. I have spent hours (literally) scouring Google searches and Spiceworks Community searches to see if a similar problem has been faced.

What I did is created a webdav server that is exposed in the DMZ. I then published the Public Calendar from my Outlook 2007 client to the webdav server. Everything worked great initially. An iPhone user can navigate to “Subscribe to Calendar” in Settings and enter the URL, and the username/password of the published webdav calendar.

Here’s where the problem comes in. Periodically and seemingly randomly, Outlook clients in our organization are prompting for the credentials of the webdav server that I published the public calendar to, from my Outlook client.

I have tried leaving my client open to eliminate the need to re-authenticate to push changes, but users still receive the prompt. I have also noticed that after someone is prompted, changes no longer are published.

My guess (and it’s only a guess) is that when a change is made to the calendar, the next Outlook client in the organization to sync with Exchange is presented with the Prompt.

Does anyone know if this is a known behavior of publishing Public Folder Calendars, or does anyone have any information that can help me either stop the prompting or create a new method of sharing the calendars? I’m open to any ideas, conventional or not.